WO2005088378A1

WO2005088378A1 - Tubular lens unit having a chromatically compensating effect

Info

Publication number: WO2005088378A1
Application number: PCT/EP2005/001798
Authority: WO
Inventors: Franz Muchel
Original assignee: Carl Zeiss Jena Gmbh
Priority date: 2004-02-28
Filing date: 2005-02-22
Publication date: 2005-09-22
Also published as: US7289271B2; US20060285219A1; DE102004009848A1

Abstract

The invention relates to a tubular lens unit that obtains a chromatically compensating effect when used with objectives having an infinite image distance and chromatic residual errors. The inventive tubular lens unit fulfils the following conditions: equation (1) CHL = CHLo - AΤ2 mT ϕT = 0, and equation (2) CHV = CHVo - 1000λ mT ϕT dl = 0, wherein CHL represents the chromatic longitudinal deviation of the tubular lens unit, CHLo represents the chromatic longitudinal deviation of the objective, CHV represents the chromatic magnification difference of the tubular lens unit, CHVo represents the chromatic magnification difference of the objective, λ represents the wavelength, mT represents the dispersion index of the tubular lens unit from mΤ = me = 1/λv wherein e is the main colour index, and λ the Abbe number, A represents the field point, dl represents the distance between the first optical element of the tubular lens unit and the entrance pupil, ϕΤ represents the refractive power, and ϕT represents the index of the respective lens in the tubular lens unit.

Description

Tube lens unit with chromatic compensating effect

The invention relates to a tube lens unit, which achieves a chromatically compensating effect when used with lenses of infinite image width and chromatic residual errors. The tube lens unit is particularly suitable for generating a color-free primary intermediate image in the imaging beam path of microscopes.

So-called ICS systems ("infinity color free system") are known from the prior art, which essentially consist of an objective lens with chromatic residual errors and infinite image width and a tube lens unit with a chromatically compensating effect. With such a combination it is achieved that, despite the chromatic residual errors of the objective, the intermediate image is created without chromatic aberrations and a largely color-accurate reproduction of microscopic object details in the entire image field is achieved.

A major disadvantage of the ICS systems known to date, however, is that the distance between the objective and the tube lens unit can only be varied within narrow limits, so that these ICS systems are bound to predetermined tube focal lengths and can therefore only be used for use in devices, for which they were designed. However, for reasons of cost it is often desirable for the user to use a tube lens unit interchangeably for several optical devices, each of which was initially only designed for a separate fixed focal length.

The invention is therefore based on the object of providing a tube lens unit of the type mentioned at the outset, which can be used for a plurality of optical devices with different tube focal lengths with the same chromatically compensating effect.

This problem is solved with a tube lens unit that fulfills the following conditions: Equation (1) CHL = CHL ₀ - A _τ ² m _τ φ _τ = 0 Equation (2) CHV = CHV ₀ - lOOOλ m _τ φ _τ di = 0

- CHL the chromatic longitude deviation of the tube lens unit;

- CHL ₀ the long chromatic aberration of the lens;

- CHV the chromatic magnification difference of the tube lens unit;

- CHV ₀ the chromatic magnification difference of the lens;

- λ of the wavelength,

- mr the dispersion number of the tube lens unit from m _τ = m _e = 1 / λv, where e is the index of the main color and v is the Abbe number; A the starting point;

- The distance of the first optical element the tube lens unit from the entrance pupil,

- φ _τ of refractive power and

- T the index of the respective lens in the tube lens unit.

For both equations, the product of the values m _τ and φ _{τ should have} the same amount.

The CHL is given in Rayleigh units RE and the CHV in h. By standardizing on Rayleigh units (IRE = λ / sinus), the CHL to be compensated has an aperture-adjusted value for lenses and thus also for tube lens units of any focal length. The CHV given in V. must have a constant value for tube lens units of any focal length.

The tube lens units must have at least one lens as compensating optical elements. In embodiments, however, it can be provided that two or more lenses are present as compensating optical elements.

If two lenses are provided, both lenses can be designed as biconvex lenses. Alternatively, a biconvex lens and a cemented element can be provided, the cemented element preferably comprising a biconcave and a convex plane lens. The flat surface should be arranged on the eyepiece side. Another embodiment of the tube lens unit according to the invention is also the Conceivable use of several putty links.

When executing the optical tube lens unit according to the invention, two cases must be distinguished.

In a first case A, the conditions given by equations (1) and (2) are met by means of two optical elements, which can each be individual lenses or cemented elements.

The compensation effect is achieved for different magnifications, specifically by combining any ICS systems with the tube lens unit according to the invention, provided that their optical elements, for example, focal lengths 1, 3 f; lf; 0,8f; ... have 0.25f.

The following is set: Ki = -A _τ ² , K ₂ = lOOOλ di, where K _n and K _{i2 are} coefficients of the first optical element and K ₂ χ and K _{22 are} coefficients of the second optical element.

The dispersion numbers itii and m _{2 of} the optical elements are determined according to

Equation (3) Kn φi x + K _i2 φ ₂ m ₂ = -CHL and equation (4) K _2i φi _λ + K ₂₂ φ ₂ m ₂ = -CHV where the values Kn, K _i2 , K ₂ ι and K ₂₂ are determined from the calculation with φi.

In a second case B, those with the chung (1) and (2) given conditions by means of a single lens. Here the requirements can be derived from equations (3) and (4) by setting for φi = φ _τ and for φ ₂ = 0.

Because of the limit values for the dispersion numbers m _τ between 20 and 90, tube lens units are only possible with limited focal lengths using only one compensating single lens. For focal lengths beyond this, a cemented element must also be used in case B.

The conditions apply:

Equation (5) Ki m _τ φ _τ = -CHL and

Equation (6) K ₂ m _τ φ-r = -CHV where m _τ = -CHL / Ki φ _τ . This also gives the value for CHV.

The special case B has so far been realized in connection with tube lenses with a focal length f = 160 mm.

With the solution according to the invention, the basis has been created that optical elements (lenses) can also be used in the tube lens unit, the focal length f of which deviate significantly from the previously customary value f = 160 mm.

It was also determined that for compensating optical elements in the tube lens unit known technical glass, for example SF6, for a focal point. width of 350 mm can be used. This makes it possible to use lenses with the chromatic residual errors CHL = -5.7 [RE] and CHV = -14.2 [° r.] For ICS optics.

The invention is explained in more detail below using two exemplary embodiments. Show

1 shows a tube lens unit according to case A with a single lens and a cemented element consisting of a biconcave and a convex plane lens,

2 shows a tube lens unit according to case B with a single lens,

3 shows another tube lens unit according to case A, but here with two cemented members.

In Fig.l the execution of a tube lens unit TL according to case A is shown in principle. Starting from the left margin of the drawing there are: the optical axis 1; the position 2 of the entrance pupil of a lens (not shown in the drawing); a first lens 3 arranged at a distance d = 126 mm from position 2 as a compensating optical element with the thickness d ₂ = 6 mm and the radii r ₃ = 62.634 mm and r ₃₂ = -117.15 mm; a cement group following at a distance d ₃ = 25.1 mm as a second compensating optical element, consisting of a biconcave lens 4 with the thickness d ₄ = 2 mm and the radii r ₄₁ = -55.033 mm and r ₄₂ = 49.048 mm and a convex plane Lens 5 with the thickness d ₅ = 3.5 mm and the radii r ₅ ι = 49.048 mm and r ₅₂ = ∞. The distance between the convex plane lens 5 of the cement group and the intermediate image plane 7 is d ₆ = 167 mm.

The entrance pupil of the lens of infinite image width, the chromatic residual error of which is to be compensated for in cooperation with the tube lens unit TL shown, is located at position 2.

The following are provided as glass: for the lens 3 N-PK51; for the lens 4 N-LAK10; for the lens 5 N-SF5.

2 shows an exemplary embodiment of the tube lens unit TL according to the invention according to the case B described above.

Starting at the left edge of the drawing, the following are provided: the optical axis 1; the position 2 of the entrance pupil of a lens (not shown in the drawing), a single lens 6 following at a distance of d ₇ = 126 mm with a thickness d ₃ = 10.9 mm and the radii r ₆ ι = 189, 417 mm and r ₆₂ = - 189.417 mm. The distance between the lens 6 and the intermediate image plane 7 is d ₉ = 167 mm. In this illustration too, the objective of infinite image width, the chromatic residual error of which is compensated by means of the tube lens unit TL shown, is not shown in the drawing. The entrance pupil of this lens is at the Pos it ion 2.

The lens 6 is made of technical glass N-BaLF4 Untitled

3 shows a further possible embodiment of the tube lens unit TL according to the case A. Here, the optical axis 1, the position 2 of the entrance pupil of an objective (not shown in the drawing) and the intermediate image plane 7 are shown.

Deviating from the embodiment according to FIG. 1, two cemented elements are present as compensating optical elements in this embodiment variant, a first of the two cemented elements consisting of two lenses 8 and 9 and the other cemented element consisting of two lenses 10 and 11.

The lens 8 is made of glass N-PSK 53 with the thickness dn = 4 mm and the radii r _B ι = 23.714 mm and r _a2 = -37.584 mm. The lens 9 consists of glass N-LASF45, has a thickness of d _i2 = 2 mm and is designed with radii r _g ι = -37.584 mm and r ₉₂ = -375.84 mm.

The lens 10 in the second cemented member consists of technical glass N-FK5, has a thickness dι ₄ = 1.5 mm and the radii rιoι = -105.93 mm and r ₁₀₂ = 6.13 mm. N-LASF45 is provided as the material for the lens 11, the thickness is ₅ = 2.5 mm, the radii are specified with rm = 6.13 mm and rn ₂ = 8.9125 mm.

The distance between position 2 of the entrance pupil and the first putty is d = ₀ = 126 mm, the distance between the two putties d _i3 = 25.82 mm and the distance between the second Kittglied and the intermediate image level 7

The object of the invention, namely to create a tube lens unit TL, which can be used with a good chromatic compensation effect for several optical devices with different tube focal lengths, is achieved, as shown, by introducing suitable focal lengths and glass materials for the elements of the tube lens unit TL.

LIST OF REFERENCE NUMBERS

1 opti see axis e

2 Position of the entrance pupil of an object ivs

3 lens

4 lens

5 lenses

6 lens

7 intermediate image plane

8 lens

9 lens

10 lens

11 lens

TL tube lens unit with distances or thicknesses 1] radii

Claims

1. tube lens unit with chromatic compensating effect for use with lenses of infinite image size and chromatic residual errors, characterized in that the tube lens unit (TL) fulfills the following condition: equation (1) CHL = CHL _σ - A _τ ² m _τ φ _τ = 0 equation ( 2) CHV = CHV ₀ - 10000 m _τ φ _τ d _x = 0 with - CHL the chromatic longitudinal deviation of the tube lens unit (TL); - CHL _{0 of} the chromatic longitudinal deviation of the objective; - CHV the chromatic difference in magnification of the tube lens unit (TL); - CHV ₀ the chromatic difference in magnification of the lens; - λ the wavelength, - m _τ the number of dispersions of the optical elements in the tube lens unit (TL) from m _τ = m _e = 1 / λv, where e is the index of the main color and v is the Abbe number; - A the starting point; - di the distance of the first optical element of the tube lens unit (TL) from the entrance pupil, - φ _τ the refractive power and - T the index of the respective lens in the tube lens unit (TL).

2. tube lens unit according to claim 1, characterized in that at least one compensating optical element is present, which is determined taking into account the equations (1) and (2) by equation (3) Kn φi m _x + K _i2 φ ₂ m ₂ ⁼ -CHL equation (4) K ₂ ι φi πti + K ₂₂ φ ₂ m ₂ = -CHV, where the values Kn, K _i2 , K ₂ ι and K _{22 are} coefficients from the calculation with φi.

3. tube lens unit according to claim 2, characterized in that a compensating optical element is provided and is designed as a biconvex lens.

4. tube lens unit according to claim 2, characterized in that two compensating optical elements are provided, of which a first element is designed as a biconvex lens and the second element as a cemented member.

5. tube lens unit according to claim 4, characterized in that the cemented member comprises a biconcave and a convex plane lens, the flat surface being arranged on the eyepiece side.

6. tube lens unit according to claim 2, characterized in that two compensating optical elements are provided and both are designed as cemented members.

-ai